Hydrogen sulfide (H2S) is a by-product produced in the process of utilizing non-renewable energy resource such as coal, natural gas, petroleum and so on. Generally speaking, a lot of H2S is generated during the processes of natural gas purification, petroleum refining, coal gas utilization and coking. H2S is a colorless poisonous gas that smells like rotten eggs, and it is also strong neurotoxin which can cause intense stimulation to mucosa.
It is not allowed to release H2S acidic exhaust into the environment, and the maximum concentration of H2S in the environment is allowably 10 mg/Nm3 according to China Environmental Standard “Health Standard for the Design of Industrial Enterprises” (TJ36-79). Claus process is the commonly-used method for treating H2S and recovering sulfur, which comprises the steps of reacting H2S with oxygen in the air to oxidize part of H2S into SO2 and further reacting H2S with SO2 in the volume ratio of 2:1 to produce sulfur. However, Claus process has many disadvantages, such as complex production process, long process flow, many equipments needed, the limitation of the process condition and high residual contaminants in tail gas. Especially, because the content of contaminants in tail gas doesn't meet the environmental protection standards, large devices for tail gas treatment are needed. Thus it can be seen that the equipments for Claus process is difficult to operate and the equipment investment and operation cost are also high. Given that about 90% of sulfur prepared by Claus process will be used to produce sulfuric acid, if H2S can be used to produce sulfuric acid directly, the equipment investment and production cost will be reduced, compared with Claus process for preparing sulfur and further preparing sulfuric acid with sulfur. The process for preparing sulfuric acid directly possesses following advantages, low equipment investment and low operation cost. At present, there is a great need for an effective method to produce sulfuric acid by using H2S, which can provide great hydrogen sulfide removal, simple process flow, and allows for economic efficiency of equipments and reasonable utilization of energy.